MD5 加密，AES加密，解密 方法

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
namespace SureSoft.Utility
{
 public class Security
 {
  public static string MD5(string value)
  {
   MD5 mD = new MD5CryptoServiceProvider();
   byte[] bytes = Encoding.Default.GetBytes(value);
   byte[] array = mD.ComputeHash(bytes);
   mD.Clear();
   StringBuilder stringBuilder = new StringBuilder();
   for (int i = 0; i < array.Length - 1; i++)
   {
    stringBuilder.Append(array[i].ToString("x").PadLeft(2, '0'));
   }
   return stringBuilder.ToString();
  }
  public static string AESEncrypt(string plainText)
  {
   Rijndael rijndael = Rijndael.Create();
   rijndael.IV = new byte[]
   {
    18,
    52,
    86,
    120,
    144,
    171,
    205,
    239,
    18,
    52,
    86,
    120,
    144,
    171,
    205,
    239
   };
   string s = "abcdabcdabcdabcdabcdabcdabcdabcd";
   rijndael.Key = Encoding.UTF8.GetBytes(s);
   MemoryStream memoryStream = new MemoryStream();
   CryptoStream cryptoStream = new CryptoStream(memoryStream, rijndael.CreateEncryptor(), CryptoStreamMode.Write);
   plainText += "=";
   cryptoStream.Write(Encoding.UTF8.GetBytes(plainText), 0, plainText.Length);
   cryptoStream.FlushFinalBlock();
   byte[] inArray = memoryStream.ToArray();
   cryptoStream.Close();
   memoryStream.Close();
   return Convert.ToBase64String(inArray);
  }
  public static string AESDecrypt(string codeText)
  {
   Rijndael rijndael = Rijndael.Create();
   rijndael.IV = new byte[]
   {
    18,
    52,
    86,
    120,
    144,
    171,
    205,
    239,
    18,
    52,
    86,
    120,
    144,
    171,
    205,
    239
   };
   string s = "abcdabcdabcdabcdabcdabcdabcdabcd";
   rijndael.Key = Encoding.UTF8.GetBytes(s);
   byte[] array = Convert.FromBase64String(codeText);
   MemoryStream memoryStream = new MemoryStream(array);
   CryptoStream cryptoStream = new CryptoStream(memoryStream, rijndael.CreateDecryptor(), CryptoStreamMode.Read);
   byte[] array2 = new byte[array.Length];
   cryptoStream.Read(array2, 0, array2.Length);
   cryptoStream.Close();
   memoryStream.Close();
   string @string = Encoding.UTF8.GetString(array2);
   return @string.Substring(0, @string.LastIndexOf("="));
  }
 }
}